Hollow core optical fiber preform with seal and method of manufacturing hollow core optical fiber therefrom

Abstract

A hollow core optical fiber preform including a seal at least partially sealing one or more of a cladding opening of a cladding tube and a capillary opening of each or some of one or more capillary tubes within a cladding interior of the cladding tube. The hollow core optical fiber preform includes a seal glass composition exhibiting a seal coefficient of thermal expansion that is within ±10% of a coefficient of thermal expansion of the cladding or a coefficient of thermal expansion of the one or more capillaries. The hollow core optical fiber perform can further include one or more metal tubes extending through the seal. The metal tubes can be placed in fluid communication with one or more sources of a gas to control gas pressure within the one or more capillary tubes and the cladding interior during a draw step to control the dimensions thereof.

What is claimed is: 
     
         1 . A hollow core optical fiber preform comprising:
 a preform longitudinal axis extending between a preform first end and a preform second end;   a cladding tube comprising (i) a cladding glass composition exhibiting a cladding coefficient of thermal expansion, (ii) a cladding interior through which the preform longitudinal axis extends, (iii) a cladding first end proximate the preform first end, (iv) a cladding second end proximate the preform second end, and (v) a cladding opening at the cladding first end;   one or more capillary tubes disposed within the cladding interior and around the preform longitudinal axis, each of the one or capillary tubes comprising (i) a capillary glass composition exhibiting a capillary coefficient of thermal expansion, (ii) a capillary longitudinal axis that is parallel to the preform longitudinal axis, (iii) a capillary interior through which the capillary longitudinal axis extends, (iv) a capillary first end proximate the preform first end, (v) a capillary second end proximate the preform second end, (vi) a capillary opening at the capillary first end, and (vii) a capillary outer surface at a capillary outer radius from the capillary longitudinal axis;   an effective core region through which the preform longitudinal axis extends, the effective core region comprising a core radius from the preform longitudinal axis that is tangential to the capillary outer surface of each of the one or more capillary tubes; and   a seal at least partially sealing one or more of the cladding opening and the capillary opening of each or some of the one or more capillary tubes, the seal comprising a seal glass composition exhibiting a seal coefficient of thermal expansion, the seal coefficient of thermal expansion within ±10% of the cladding coefficient of thermal expansion or the capillary coefficient of thermal expansion.   
     
     
         2 . The hollow core optical fiber preform of  claim 1 , wherein the cladding glass composition and the capillary glass composition are the same. 
     
     
         3 . The hollow core optical fiber preform of  claim 1 , wherein the seal directly contacts and at least partially seals the cladding opening. 
     
     
         4 . The hollow core optical fiber preform of  claim 1 , wherein the seal directly contacts and at least partially seals the capillary opening of each of the one or more capillary tubes. 
     
     
         5 . The hollow core optical fiber preform of  claim 1 , wherein the seal glass composition comprises at least 10 mol % of one or more of Cu 2 O and CuO. 
     
     
         6 . The hollow core optical fiber preform of  claim 1 , wherein the seal coefficient of thermal expansion is within ±10% of the cladding coefficient of thermal expansion. 
     
     
         7 . The hollow core optical fiber preform of  claim 1 , wherein the seal coefficient of thermal expansion is within ±10% of the capillary coefficient of thermal expansion. 
     
     
         8 . The hollow core optical fiber preform of  claim 1 , wherein the seal coefficient of thermal expansion is within a range of from 10×10 −8  K −1  to 120×10 −8  K −1 . 
     
     
         9 . The hollow core optical fiber preform of  claim 1 , wherein
 the cladding glass composition exhibits a cladding softening point,   the capillary glass composition exhibits a capillary softening point,   the seal glass composition exhibits a seal softening point; and   the seal softening point is less than the cladding softening point or the capillary softening point.   
     
     
         10 . The hollow core optical fiber preform of  claim 1  further comprising:
 one or more metal tubes extending through the seal, each of the one or more metal tubes comprising (i) a first tube end disposed outside of the cladding interior, (ii) a second tube end disposed within the cladding interior, and (ii) an outer surface at least partially facing the seal. 
 
     
     
         11 . The hollow core optical fiber preform of  claim 10 , wherein
 the seal at least partially seals the cladding opening, and   the second tube end of at least one of the one or more metal tubes is disposed within the cladding interior and outside of the capillary interior of all of the one or more capillaries.   
     
     
         12 . The hollow core optical fiber preform of  claim 11  further comprising:
 a silica guide tube disposed within the cladding interior and through which the at least one of the at least one or more metal tubes extends, the silica guide tube separating the at least one of the at least one or more metal tubes from the capillary outer surface of each of the one or more capillaries. 
 
     
     
         13 . The hollow core optical fiber preform of  claim 12  further comprising:
 a glass frit disposed on the outer surface of the at least one of the one or more metal tubes between the second tube end and where the outer surface faces the silica guide tube. 
 
     
     
         14 . The hollow core optical fiber preform of  claim 10 , wherein
 the seal at least partially seals the capillary opening of each or some of the one or more capillaries, and   the capillary interior of the at least partially sealed ones of the one or more capillaries receives the second tube end of a different one of the one or more metal tubes.   
     
     
         15 . The hollow core optical fiber preform of  claim 14  further comprising:
 glass frit disposed between the capillary outer surface of at least one of the at least partially sealed ones of the one or more capillaries and the outer surface of the metal tube disposed therein. 
 
     
     
         16 . The hollow core optical fiber preform of  claim 10 , wherein each of the one or more metal tubes is in fluid communication with a source of gas. 
     
     
         17 . The hollow core optical fiber preform of  claim 10 , wherein the seal further comprises a polymer dispersed within the seal glass composition disposed around the one or metal tubes. 
     
     
         18 . A method of manufacturing a hollow core optical fiber comprising:
 a drawing step comprising drawing a hollow core optical fiber from a hollow core optical fiber preform comprising:
 a preform longitudinal axis extending between a preform first end and a preform second end; 
 a cladding tube comprising (i) a cladding glass composition exhibiting a cladding coefficient of thermal expansion, (ii) a cladding interior through which the preform longitudinal axis extends, (iii) a cladding first end proximate the preform first end, (iv) a cladding second end proximate the preform second end, and (v) a cladding opening at the cladding first end; 
 one or more capillary tubes disposed within the cladding interior and around the preform longitudinal axis, each of the one or capillary tubes comprising (i) a capillary glass composition exhibiting a capillary coefficient of thermal expansion, (ii) a capillary longitudinal axis that is parallel to the preform longitudinal axis, (iii) a capillary interior through which the capillary longitudinal axis extends, (iv) a capillary first end proximate the preform first end, (v) a capillary second end proximate the preform second end, (vi) a capillary opening at the capillary first end, and (vii) a capillary outer surface at a capillary outer radius from the capillary longitudinal axis; 
 an effective core region through which the preform longitudinal axis extends, the effective core region comprising a core radius from the preform longitudinal axis that is tangential to the capillary outer surface of each of the one or more capillary tubes; 
 a seal at least partially sealing one or more of the cladding opening and the capillary opening of each or some of the one or more capillary tubes, the seal comprising a seal glass composition exhibiting a seal coefficient of thermal expansion, the seal coefficient of thermal expansion within ±10% of the cladding coefficient of thermal expansion or the capillary coefficient of thermal expansion; and 
 one or more metal tubes extending through the seal, each of the one or more metal tubes comprising (i) a first tube end disposed within the cladding interior, (ii) a second tube end dispose outside of the cladding interior, and (iii) an outer surface at least partially facing the seal, 
 wherein, (i) the seal at least partially seals the cladding opening, and the first tube end of at least one of the one or more metal tubes is disposed within the cladding interior and outside of the capillary interior of all of the one or more capillaries, (ii) the seal at least partially seals the capillary opening of each or some of the one or more capillaries, and, the capillary interior of the at least partially sealed ones of the one or more capillaries receives a second end of a different one of the one or more metal tubes, or (iii) both (i) and (ii). 
   
     
     
         19 . The method of  claim 18  further comprising:
 a gas flow step comprising flowing gas from one or more sources of the gas through the one or more metal tubes. 
 
     
     
         20 . The method of  claim 18  further comprising:
 a sealing step, occurring before the drawing step, comprising melting a piece of the seal glass composition over (i) the cladding opening, (ii) the capillary opening of each or some of the one or more capillary tubes, or (iii) both (i) and (ii), with the one or more metal tubes extending through the seal glass composition.